1. Field of the Invention
The present invention relates to switches for a vehicle (hereinafter referred to as vehicle switches) that are incorporated mainly in a vehicle and used to detect whether a door thereof is opened or closed.
2. Background Art
It is widely applied to control turning on and off the lighting apparatuses in a vehicle cabin, by using a vehicle switch incorporated in the door part thereof according to opening and closing operation of the door. In many cases, such a vehicle switch is incorporated in a place exposed to water drops, such as rain, when the door is open; therefore, the vehicle switch is protected from water by a rubber cover or other parts. A description is provided of such a conventional vehicle switch in reference to FIGS. 6 to 8B.
FIG. 6 is a sectional view of a conventional vehicle switch. FIG. 7 is an exploded perspective view thereof. Into outer case 31 that is made of an insulating resin and has through-hole 31A through the top face thereof, inner case 32 is fitted and fixed. Fixed contacts (hereinafter referred to as contacts) 33 and 34 made of metal are embedded in the right and left portions of the inner wall of inner case 32 so that the contacts are opposed to each other.
Operating body 35 made of an insulating resin is housed in inner case 32 so as to be vertically movable. Operating portion 35A at the top end of operating body 35 projects upwardly from through-hole 31A. Both ends of substantially U-shaped movable contact (hereinafter referred to as a contact) 36 that is made of metal and fitted into operating body 35 makes resilient contact with corresponding one of contacts 33 and 34. Contacts 33 and 34 are electrically coupled via contact 36. In this manner, a switch contact is formed.
Coil-like spring 37 is installed between the outer bottom face of operating body 35 and the inner bottom face of inner case 32 so as to slightly be contracted. Spring 37 urges operating body 35 upwardly. Elastic cover (hereinafter referred to as a cover) 38 is substantially shaped like a dome and made of a thin rubber. Cover 38 is attached onto the outer top face of outer case 31 by mounting plate 39 made of a metal plate. Covering through-hole 31A and operating body 35A, cover 38 prevents water or dust from entering into the switch from the gap between outer case 31 and operating body 35. In this manner, the vehicle switch is structured.
This vehicle switch is mounted on the chassis, for example, of a door part of a vehicle. Terminals 33A and 34A of contacts 33 and 34 projecting downwardly from the outer bottom face of inner case 32 are coupled to room lamps, for example, by leads (not shown) via electronic circuits (not shown) of the vehicle.
Next, a description is provided of the operation of this vehicle switch. Closing a door of the vehicle as shown in the sectional view of FIG. 8A brings pressing portion 40 of the door into contact with cover 38, thus pressing the top end of operating portion 35A of operating body 35 while deforming cover 38. Then, while contracting spring 37, operating body 35 moves downwardly, and both ends of contact 36 fitted into operating body 35 leave contacts 33 and 34 as shown in FIG. 8B. This operation turns off the switch contact, thus turning off the room lamp, for example.
In contrast, opening the door brings pressing portion 40 out of contact with cover 38, thus removing depression to operating body 35. For this reason, cover 38 is restored to the state of FIG. 8A by the elastic restoring force thereof. Additionally, the urging force of spring 37 moves contact 36 upwardly along with operating body 35. This operation brings both ends of contact 36 in resilient contact with contacts 33 and 34, thus turning on the switch contact and turning on the room lamp, for example. As described above, the vehicle switch detects whether the door is opend or closed: opening the door turns on the room lamp; and closing the door turns off the room lamp. Such a vehicle switch is disclosed in Japanese Patent Unexamined Publication No. 2003-146077.
However, used for water-proof and dust-proof cover 38 in the conventional vehicle switch is a rubber or other materials that has a large friction coefficient and thus does not slide easily. For this reason, when pressing portion 40 of a door is brought into not perpendicular but oblique contact with cover 38 as shown in FIG. 8B, cover 38 is deformed into a distorted shape as it is pressed. Repeating such operations may break cover 38 and make the inside of the switch water-proof and dust-proof insufficiently.